


Type II Supernova

by laudatenium



Series: Massive [1]
Category: Marvel 616, The Avengers (Marvel) - All Media Types
Genre: Heavy Angst, IT'S NOT A HAPPY ENDING NOT AT ALL, Implied/Referenced Character Death, M/M, Mutual Pining, Science Jargon, Space Nerd Tony Stark, also part of my one-woman campaign to make marvel more scientifically accurate, it's sad and i'm mean but i'm warning you now
Language: English
Status: Completed
Published: 2016-03-30
Updated: 2016-03-30
Packaged: 2018-05-30 04:11:28
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 2,406
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6408253
Author URL: https://archiveofourown.org/users/laudatenium/pseuds/laudatenium
Summary: <blockquote class="userstuff">
              <p>It's not a suicide note, but Steve might tell you it is.</p>
            </blockquote>





	Type II Supernova

**Author's Note:**

> Fuuuck, why does studying for astronomy give me Tony feels? Stupid question.

_“We are made of stardust,”_ Tony begins.

Steve nods, waits. The recording continues.

 _“There are many types of stars,”_ the Tony on the screen waxes, because that’s what he does. No matter how long Steve has known Tony, nothing can hold a candle to space and stars and distant worlds. Nothing. Must be something to do with the wonder of discovery. _“Our sun is actually rather boring, far as stars go. It’s very low mass compared to some. Most of the stars we can see from Earth are larger, brighter, have higher masses. Much more interesting. Were we to look at Earth from only ten parsecs away – remember, that’s only about thirty-three light-years – our sun would only just be visible to the naked eye. Human history wants to make our solar system out to be exemplary – and there are several ways it is, life being one of the bigger oddities – but our star, our central point, that thing that made us possible? Eh, it’s average.”_

He has to chuckle at that. That is the reason Tony made the joke, in the hopes that Steve would laugh and relax. He’s always been more than capable of putting Steve at ease. Had Tony made the joke in person, it might have worked. But Tony isn’t here; only this video that had been made in this same lab, the timestamp saying only seven hours ago. So the tension remains in Steve’s shoulders, his fingers remain clutched around the edge of his shield.

 _“Stars are powered by nuclear fusion. Ionized hydrogen atoms –which are really just naked protons – crash into each other, releasing deuterons and positrons and neutrinos, positrons clash with free electrons, releasing gamma rays, and deuterons clash with protons, making helium-3 atoms. When two atoms of helium-3 collide, the result is ionized helium-4, plus two spare protons that go back into the fray. But helium-4 stays the way it is.”_ Tony pauses, chewing it over. _“Well, actually, no, that’s the wrong way to phrase it. Helium-4 is stable, but it can continue to fuse. Three helium-4s will eventually form carbon-12.”_

Steve chews on his cheek, waiting. He wants to snap at Tony to get on with it, but he’s had enough of yelling at computers over the years.

He just has to wait, because not matter how long-winded, Tony would always get to a point eventually.  And there has always been something beautiful about Tony speaking about science, even if Steve doesn't always understand it.  Something about the light in his eyes.

 _“So here’s where things get complicated,”_ and Steve has to refrain from yelling that this is already complicated. _“In a star like our sun, carbon-12 is about as far as nuclear fusion will go. Hydrogen will fuse in our sun’s core for about ten billion years before temperatures increase enough to fuse helium, which they will have to, because by that time all of the hydrogen in the sun’s core will be helium. There are a ton of changes in the non-burning parts of the star, but let’s just stay focused on the core, shall we? For a much shorter time, comparatively, the sun will fuse helium, until the core is completely composed of carbon ash. There are a handful of heavier elements here and there, but for all intents and purposes, the core is completely carbon. Helium burning is a violent process, prone to giving off large flashes of very intense energy, and the star just can’t cope. The outer layers are stripped away and ejected, leaving only the naked core made of white-hot carbon. This is called a white dwarf, which will cool very slowly until it becomes nothing but a lump of charcoal floating in space.”_

As far as Steve always heard, stars blew up, but he’s sure Tony will get to that.

 _“Now, a white dwarf can continue to be active. It can re-gain matter, or collide with another white dwarf. But basically, if mass gets enough to where the white dwarf can begin to fuse carbon, it will explode violently, into what we call a type I supernova. Pretty flash of light, or catastrophic, depending on your view.”_ Tony grins a tad manically, and Steve thanks whatever god is listening that Tony has always been on the side of angels. _“But after a while – months or decades, depending – all the star’s matter will cool and become interstellar matter, which is just dark clouds of gas and dust floating between the stars. It is from this dust that new stars are made – as well as Earth and all things who inhabit it. Every atom on Earth that isn’t formed in a lab was born in the belly of a star billions of years ago. So, us carbon-based lifeforms owe our lives to stars that died many eons past._

_“But what I want to tell you about isn’t low mass stars like our sun, but high mass ones – maybe eight times the mass of our sun, and up. Now, stars heat up because energy gets trapped, which occurs because of gravity pulling mass in on itself. Well, it’s far more complicated than that, but suffice to say, the higher the mass, the more gravity pulls that mass in, the higher the density gets, and the more likely atoms are to crash into each other, which as you know, releases energy. So, the more mass, the more energy. So rather naturally, bigger stars are brighter but live shorter lives because everything’s accelerated.”_

The urge to tell Tony to accelerate is almost unbearable.

_“Now, remember how I said that our sun is never going to make atoms larger than carbon in large quantities? Well, that’s not so with these high mass stars, because the temperatures are high enough to sustain helium fusion and onward. The temps aren’t enough for large-scale carbon fusion, but there is a process called helium capture which bypasses that. Basically, a helium atom will fuse to a carbon atom to make oxygen. And so on. Oxygen, then neon, magnesium, silicon, sulfur, argon, calcium, titanium, chromium, and then of course, iron.”_

Tony’s tone has shifted, and Steve can tell he’ll be getting closer to the point now. Steve doesn’t really want to know, not about this, doesn’t think he can bear it. But he has to know, because Tony knew going in what the result would be.

_“Iron is an interesting element. For the sake of this discussion, it marks a dividing line on the periodic table. All lighter elements than iron produce energy as a by-product of fusion. Any element heavier than iron needs energy to actually fuse, but when they split or shed pieces, they release energy. That’s fission. Iron is like nature’s damper, producing next to no energy when either split or fused. Iron-52 atoms will actually continue helium capture, making nickel-56. But it takes copious amounts of energy to form, and it’s unstable. It will decay into cobalt-56, then iron-56. Good ol’ iron-56. The most stable isotope of the most stable element. You’ll have to forgive me, but for years I’ve found it hi-larious that Iron Man is considered the most unstable Avenger.”_

“You’re not,” Steve whispers, far too softly. Then he curses, because he swore to himself that he wasn’t going to talk to the screen. “You’ve been the most reliable. It’s the rest of us who skipped out.”

But it’s too late for that.

 _“But I’ll let you marvel at the iron-y another time,”_ and Steve groans at Tony’s shit-eating grin. _“The thing is, inactivity isn’t really something you want in a shell of burning gas. Who’d’a thought? Fusion into anything larger than iron eats up a bunch of energy, so it doesn’t last. Well, neutron capture occurs on a small scale, but like I said, small. Iron is the wet rag on the internal fire of a large star. Without energy production, the equilibrium that keeps the star stable is gone. Gravity becomes stronger than the outward press of energy, and the star implodes. The process of fusion is reversed, as atoms in the very center of the core are split by gamma photons, and the massive thermal energy is absorbed. Protons and electrons are fused into neutrons and neutrinos. Neutrinos escape, and neutrons are pressed together. Eventually, the contracting ball can’t contract any more, and explodes outward, scattering gas and heavy elements in an ionized cloud that disperses over time. This is the core-collapse, or type II supernova.”_

Tony pauses. _“It’s the most beautiful thing,”_ he says, his voice suddenly hoarse. _“The death of a star.”_

Steve doesn’t want to hear any more.

How could Tony have been so calm about this?

He had known. He had known this morning, as everyone engaged in the usual breakfast banter. They’d been anticipating this showdown for weeks, so the atmosphere has been slightly more subdued than usual, but nothing out of place. Thor chomping on his usual smelly canned Scandinavian fish and eight hard-boiled eggs, and Clint acting all offended over everyone eating his “babies”. It was a really shitty old joke that never failed to garner a laugh. Tony happily chatting away with everyone, and begging Steve to make waffles like every morning. Steve hadn’t wanted to be bothered, so Tony’d had sugar cereal.

Could he turn back the clock, Steve would have cracked open the waffle-maker and served up a platter of chocolate chip waffles buried beneath a mountain of whipped cream and strawberry compote. Just the way Tony always wanted them. He would have teased Tony about rotting his teeth and would have ruffled his hair, and maybe would have screwed his courage and finally tried to find out what Tony’s mouth tasted like.

But he doesn’t know what Tony’s mouth tasted like, and Tony went into battle with a stomach full of sugar cereal, knowing he wouldn't come out.

 _“Just. Stars.”_ Tony laughs slightly, a heartbreaking sound. _“They really put things into perspective, don’t they? We’re nothing, really. Insignificant in the vast void of this universe and time. I gotta say, the only thing that ever made me feel as small as staring up at the stars was falling in love. Especially when that person you love can make you feel both massive and like nothing.”_

Tony sighs wistfully on the screen, and the sliver of ice lodged deep in Steve's lungs grows.

 _“Love is a funny thing, because it’s everything to individuals, but it’s nothing to the universe. The universe doesn’t care when it takes someone you love from you.”_ His face wrinkles, remembering. Steve doesn’t know who, but it could be any one of so many people Tony has lost. His mother. Rumiko. Happy. Even Steve for a while. _“Even in the face of just Earth, just this Earth in just this universe, one person’s love is inconsequential in the face of seven point three billion people.”_

Steve wants to scream, shut off the recording, run away, to not have to listen anymore. But he does have to listen. He gave Tony his word.

 _“I’m sorry, Steve. But I know what I’m doing. And I know you won’t approve. That’s fine. It won’t be the first time. But it will be the last.”_ Recording Tony pauses, then leans closer into the camera. _“It’s the only way.”_

“It wasn’t,” Steve growls.

Tony cocks his head. _“See, I paused there to let you say ‘It wasn’t’ because that is exactly what you will say. ‘Cause you’re stubborn as a mule, and see reason just as well as one. This isn’t some big dramatic ‘pay attention to me’ move. Nothing anyone can do could have prevented this. Just a well-calculated sacrifice.”_

Steve clenches his hands more. “Bullshit,” he says, and his voice cracks. His face is wet, and the salt from his tears makes his eyes itch. But he can’t wipe his face, not yet.

Tony’s blue eyes are tired and sorrowful and apologetic, which steams Steve to no end, because the way Tony is treating this, Steve can’t be mad at him. Were he obstinate, Steve could let anger dull the pain. But no, Tony obviously predicted how Steve would respond, and is being annoyingly understanding.

_“And you’re gonna stay that that’s bullshit, but you know that’s not gonna change anything. There’s just two things left I need to tell you, and I need you to understand. Iron is the last stable element that forms in a large mass star’s core before supernova. But do you know what forms out of the dust of a supernova? New stars. Stellar dust to stellar dust. Matter never dies. It is only reborn into something else. Something greater._

_“I’m not meant to burn out slowly like a white dwarf. I know myself, and I know that’s just not in the cards for me. I’m meant to die in a dramatic flash of light. And we’re long overdue for a supernova._

_“And Steve? I know it doesn’t matter, but I loved you,”_ Tony adds, like an afterthought, easy as breath. _“I always loved you.”_

Steve waits for more, but Tony just shoots the camera one last wavering smile until the screen goes blue. Then it goes black as his shield slices through the surface and shatters the glass.

It feels good, for a millisecond, because the sparking pieces of the screen remind him of the slivers of shattered glass rolling around in the cavity where his heart used to reside.

He takes a moment to breathe, then walks with mechanical movements over towards the sink. He splashes cold water on his face and scrubs his eyes vigorously, but when he looks around for the mirror he doesn’t find one. Of course. Tony never liked mirrors. Steve has to make do with wiping damp paper towels under his eyes and hoping they don’t look too bloodshot. But they probably will, and he finds doesn’t care.

Steve grabs his cowl, traces his fingers along the wings for a moment before donning it. Then he squares his shoulders and leaves the lab, bound for the area where they do press briefings. Because like hell he’ll let anyone else tell the world that Tony Stark is dead.

And he’ll say Tony Stark. Not Iron Man.

Iron will float among the stars until it forms a new one. Iron Man will fly again. He’ll make sure of it.

But no amount of captured stardust will ever bring Tony back to him.

**Author's Note:**

> Ummm, I thought of a sequel, and another. I should not.


End file.
